U.S. patent number 6,713,168 [Application Number 09/904,126] was granted by the patent office on 2004-03-30 for fire retardant wood composite materials.
This patent grant is currently assigned to J.M. Huber Corporation. Invention is credited to Feipeng Liu, Nian-hua Ou.
United States Patent |
6,713,168 |
Liu , et al. |
March 30, 2004 |
Fire retardant wood composite materials
Abstract
The invention relates to a fire retardant oriented strand board
composite material comprising a mixture of wood strands, at least
one organophosphorus ester, at least one polymeric binder resin,
and a wax. In a process embodiment of the present invention this
mixture is consolidated under heat and pressure to form an oriented
strand board composite panel, whereby during consolidation the
organophosphorus ester chemically interacts with the polymeric
binder to provide cross-linking between the binder and the
organophosphorus ester.
Inventors: |
Liu; Feipeng (Statham, GA),
Ou; Nian-hua (Watkinsville, GA) |
Assignee: |
J.M. Huber Corporation (Edison,
NJ)
|
Family
ID: |
25418603 |
Appl.
No.: |
09/904,126 |
Filed: |
July 12, 2001 |
Current U.S.
Class: |
428/292.4;
428/297.4; 428/298.1; 428/537.1; 524/13; 524/14; 524/417 |
Current CPC
Class: |
B27N
9/00 (20130101); D21J 1/00 (20130101); Y10T
428/249942 (20150401); Y10T 428/31591 (20150401); Y10T
428/249925 (20150401); Y10T 428/24994 (20150401); Y10T
428/31989 (20150401) |
Current International
Class: |
B27N
9/00 (20060101); D21J 001/00 () |
Field of
Search: |
;428/532,292.4,297.4,298.1,107 ;524/13,14,417 ;525/410,390,414 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Seidleck; James J.
Assistant Examiner: Bissett; Melanie
Attorney, Agent or Firm: Nieves; Carlos Goodrich; David
Mitchell
Claims
We claim:
1. A wood composite material that is an oriented strand board
comprising: (i) an organophosphorus ester compound, (ii) a polymer
binder resin, and (iii) about 0.5 wt % to about 2.5 wt % wax,
wherein said composite material achieves a limiting oxygen index in
the range of about 26 to about 40, an average thickness swelling in
the range of about 7% to about 15%, and said composite material has
a fire spread rating of greater than about 25 and less than about
75.
2. The fire retardant oriented strand board composite material
according to claim 1, wherein the organophosphorus ester has the
formula: ##STR2##
and R.sub.1, R.sub.2 and R.sub.3 are independently either alkyl or
aryl chains having hydroxyl, carboxylic or both hydroxyl and
carboxylic functionality.
3. The fire retardant oriented strand board composite material
according to claim 1 wherein the at least one organophosphorus
ester is at least one ester selected from the group consisting of
diethyl-N, N-bis(2-hydroxyethyl) aminomethyl phosphate; dimethyl
methyl phosphate; diethyl-N, N-bis(2-hydroxyethyl) aminoethyl
phosphonate; dimethyl-N, N-bis(2-hydroxyethyl) aminomethyl
phosphonate; dipropyl-N,N-bis(3-hydroxypropyl) aminoethyl
phosphonate; and dimethyl-N, N-bis(4-hydroxybutyl) aminomethyl
phosphonate.
4. The fire retardant oriented strand board composite material
according to claim 1, wherein the organophosphorus ester is at
least one ester selected from the group consisting of
diethyl-N,N-bis(2-hydroxyethyl) aminomethyl phosphate and dimethyl
methyl phosphate.
5. The fire retardant oriented strand board composite material
according to claim 1 comprising from about 5 wt % to about 30 wt %
of the organophosphorus ester compound.
6. The fire retardant oriented strand board composite material
according to claim 2 wherein said polymeric binder is selected from
the group consisting of isocyanates, phenol-formaldehydes, and
melamine urea formaldehyde.
7. The fire retardant oriented strand board composite material
according to claim 1 wherein the composite material comprises about
5 to about 30 wt % of the organophosphorus ester compound and about
3 to about 20 wt % of the polymeric binder.
8. The fire retardant oriented strand board composite material
according to claim 1 wherein the composite material comprises about
5 to about 10 wt % of the organophosphorus ester and about 3 to
about 10 wt % of the polymeric binder.
9. The fire retardant oriented strand board composite material
according to claim 1, wherein the at least one organophosphorus
ester forms cross-links between polymer chains of the at least one
polymeric binder resin.
Description
FIELD OF THE INVENTION
This invention relates to fire retardant wood composite materials
for use in the commercial and residential building industry. In
particular, organophosphorus fire retardant chemicals are
incorporated into wood composite materials to achieve a high level
of fire retardancy, while maintaining the quality and strength of
the wood composite.
BACKGROUND OF THE INVENTION
In the past, the forest product industry has continued to seek and
develop cost-effective fire retardant chemicals for use in wood
composite materials, such as particleboard, fiberboard, oriented
strand boards, agricultural straw board and inorganic building
materials such as gypsum boards. Typically, acceptable fire
retarding performance is achieved by manufacturing and
incorporating a fire retardant compound in the wood composite.
Although processes for preparing fire retardants for wood composite
materials are known, there is a continuing need for a more
cost-effective, environmentally beneficial means to satisfy flame
retardant specifications, while maintaining the quality and
strength of the wood composite materials.
Prior attempts to incorporate fire retardant organic phosphate
esters into wood composite materials have met with little success,
primarily because reactions between the phosphate ester and
isocyanate binder can be unpredictable and can lead to pre-curing
and interfacial strength loss during composite manufacture.
Furthermore, some phosphate esters are easily decomposed under the
hot press conditions during the manufacture of wood composites.
Finally, phosphate esters generally tend to leach out of the
composite over time, thereby making these phosphate esters
undesirable and environmentally unfriendly fire retardant
additives.
BRIEF SUMMARY OF THE INVENTION
In one object of the present invention, the invention includes a
fire retardant wood composite material comprising a polymeric
binder, and characterized in that the material further comprises at
least one organophosphorus ester.
A further object of the present invention is a process for
preparing a fire retardant oriented strand board composite
material. A first step in this process is coating wood strands or
flakes with at least one polymeric binder, wax, and at least one
organophosphorus ester and forming a mat of the coated wood strands
or flakes. A further step in this process is compressing the mat
under heat and pressure to form an oriented strand board composite
panel, characterized in that upon compression the at least one
organophosphorus ester forms cross-links between polymer chains of
the at least one polymeric binder resin.
Preferably, the organophosphorus ester has the formula:
##STR1##
wherein R.sub.1, R.sub.2 and R.sub.3 are either alkyl or aryl
chains having hydroxyl, carboxylic or both hydroxyl and carboxylic
functionality.
An object of the present invention is to provide a fire retardant
wood composite material wherein an effective amount of
organophosphorus fire retardant chemicals are incorporated into a
wood composite material to form a wood composite material having a
high level of fire retardancy.
Another object of the present invention is to provide wood
composite materials comprising organophosphorus fire retardant
additives, characterized in that the organophosphorus fire
retardant additives cross-link with the polymeric binders and wood
composite materials, thereby preventing leaching of the
organophosphorus materials from the wood composite material. In
addition, this cross-linking ameliorates the strength loss that
typically accompanies the addition of functional additives like
fire retardants, and also improves the dimensional stability and
durability of the composite panel.
Accordingly the wood composite materials prepared according to the
present invention have a limiting oxygen index of about 26 to about
40, an average thickness swelling in the range of about 7% to about
15%, and a fire spread rating of greater than about 25 and less
than about 75.
Other objects, features and advantages will be readily apparent
from the following detailed description of preferred embodiments
thereof.
All parts, percentages and ratios used herein are expressed by
weight unless otherwise specified. All documents cited herein are
incorporated by reference. Concentrations of the polymer resins,
waxes, fire retardants and other additives that are included in the
wood composite materials of the present invention are calculated
based on the weight of the over-dried wood flakes or strands.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a fire retardant wood composite
materials that incorporate organic phosphorus esters as a fire
retardant, as well as processes for their manufacture.
As used herein, "wood" is intended to mean a cellular structure,
with the cell walls being composed of cellulose and hemicellulose
fibers bonded together by lignin material, which functions as a
type of polymer cement.
By "wood composite material" it is meant a composite material that
comprises wood and one or more other additives, such as adhesives
or waxes. Non-limiting examples of wood composite materials include
oriented strand board ("OSB"), waferboard, chipboard, particle
board, fiberboard, and plywood. As used herein, "flakes",
"strands", and "wafers" are considered equivalent to one another
and are used interchangeably.
Preferred wood composite materials utilized in this invention are
derived from naturally occurring hard or soft woods, singularly or
mixed, whether such wood is dried (having a moisture content of
between 2 wt % and 12 wt %) or green (having a moisture content of
between 30 wt % and 200 wt %). Preferably, the wood composite
materials comprise dry wood parts having a moisture content of
about 3 to 8 wt %. Typically, the raw wood starting materials,
either virgin or reclaimed, are cut into strands, wafers or flakes
of desired size and shape, which are well-known to one of ordinary
skill in the art.
In the commercial manufacture of OSB panels, after the strands are
cut they are dried to a moisture content of about 2 wt % to 5 wt %
and then coated with a polymeric thermosetting binder resin and wax
additive. Conventionally, the binder, wax and any other additives
are applied to the wood materials by one or more spraying, blending
or mixing techniques. One such technique is to spray the wax, resin
and additives upon the wood strands as the strands are tumbled in a
drum blender. Binder resin and various additives applied to the
wood materials are referred to herein as a coating, even though the
binder and additives may be in the form of small particles, such as
atomized particles or solid particles, which do not form a
continuous coating upon the wood material. Fire retardant chemicals
are incorporated either before, during or after coating of the wood
materials. These fire retardant chemicals may be sprayed on the
wood materials, or in the alternative, premixed with the binder
and/or wax additive. The blended mixture is formed into either a
random mat or oriented multi-layered mats. In particular, the
coated wood materials are spread on a conveyor belt in a series of
alternating layers, where one layer will have the flakes oriented
generally in line with the conveyor belt, and the succeeding layer
oriented generally perpendicular to the belt, such that alternating
layers have coated wood materials oriented in generally a
perpendicular fashion. Subsequently, the formed mats will be
pressed under a hot press machine which fuses and binds together
the wood materials to form consolidated OSB panels of various
thickness and size. Preferably, the panels of the invention are
pressed for 2-10 minutes at a temperature of about 175.degree. C.
to about 240.degree. C. The resulting composite panels will have a
density in the range of about 40 to about 50 pcf (ASTM D1037-98)
and a thickness of about 0.25 (1/4") to about 1.5 (11/2")
inches.
Various polymeric resins, preferably thermosetting resins, may be
employed as a binder for the wood flakes or strands. Preferred
polymeric binders include isocyanate resin, urea-formaldehyde,
phenol formaldehyde, melamine formaldehyde and the co-polymers
thereof. More preferably, the polymeric binders are
4,4-diphenyl-methane diisocyanate ("MDI") and melamine urea
formaldehyde ("MUF"). MDI has NCO-- functional groups that can
react with other organic functional groups to form polymer groups
such as polyurea, --NCON--, and polyurethane, --NCOON--. MUF is a
widely-used and cost effective polymeric binder, but is less
water-resistant than MDI. Typically up to 50 wt % of the MUF binder
is melamine, which is added to improve water-resistance. Suitable
commercial MUF binders are the LS 2358 and LS 2250 products from
the Dynea corporation.
Also suitable for use as polymeric binders are phenol-formaldehyde
resins such as resol-type resins and novolac-type resins. These
resins are produced by a reaction between phenol (C.sub.6 H.sub.6
O) and formaldehyde (CH.sub.2 O). In the case of resols, the
synthesis of phenol and formaldehyde occurs in the presence of an
alkaline catalyst, typically a sufficient amount of alkaline
catalyst (e.g., sodium hydroxide or potassium hydroxide) is added
to bring the pH of the resin to between 10 and 12. Higher pH
environments do increase the cure rate of the polymer resins,
however, these environments can also cause the organophosphorus
esters (discussed in greater detail below) to decompose under hot
press conditions.
Novolacs are produced similarly to resols, e.g., by reacting
phenols and formaldehydes, but in the presence of an acid catalyst
rather than an alkaline catalyst. Preferably a curing agent is
added to increase the amount of cross-linking in the polymer, or
alternatively, additional amounts of formaldehyde may be added
either before or during the reaction between phenols and
formaldehydes.
Resols and novolacs can also be distinguished by their molar ratio
of formaldehyde to phenol: for resols the molar ratio of
formaldehyde to phenol is larger than one, typically the ratio is
between 1.6 and 2.2, while in novolacs, the same molar ratio is
less than one, before adding hardener.
The binder level is preferably in the range of about 3 to about 20
wt %, more preferably about 3 to about 10 wt %.
A wax additive is commonly employed to enhance the resistance of
the OSB panels to absorb moisture. Preferred waxes are slack wax or
an emulsion wax. The wax loading level is preferably in the range
of about 0.5 to about 2.5 wt %, based upon the oven-dried wood
weight.
In accordance with a preferred embodiment of this invention, an
organophosphorus ester is employed as a fire retardant chemical
additive during the manufacture of OSB panels. The preferred
organic phosphorous esters include a mono-, di- or tri-hydroxyl or
carboxylic functional group which serves as a potential reaction
site with the organic polymeric binder. In particular, preferred
organic phosphate esters are oligomeric phosphonate, diethyl N,N
bis[2-hydroxyethyl] aminomethylphosphonate and dimethyl
methylphosphonate, respectively sold under the tradenames
Fyrol.RTM. 51, Fryol.RTM. 6 and Fyrol.RTM. DMMP, by Akzo Nobel
Chemical, Inc. Fyrol.RTM.51 and Fryol.RTM. 6 are advantageous
because both have hydoxyl functional groups for reacting with MDI
or MUF, while Fyrol.RTM. DMMP has the advantage of having a high
phosphorous ester content and at the same time has a low viscosity
that facilitates easy processing.
However, because Fryol.RTM. 51 has a high viscosity (approximately
30, 000 mPa.s, it is not suitable for application by spraying.
However, it may be combined with other compounds having lower
viscosity to prepare an organophosphorus fire retardant solution
that is suitable for spraying. For example, Fryol.RTM. 51 may be
mixed with Fryol.RTM. DMMP, which has a viscosity of 4 mPa.s, to
form an organophosphorus solution. It is preferred that these
compounds be mixed at a ratio of Fryol.RTM. 51: Fryol.RTM. DMMP of
from about 1:1 to about 4:1.
The organophosphorus ester loading level is in the range of about 5
to about 30 wt %, preferably about 5 to about 20 wt %, more
preferably about 5 to about 10 wt %, based upon the oven-dried wood
weight.
Without intending to be limited by theory, it is believed that
these organophosphorus esters not only function as fire retardants,
but also act as cross-linking agents to increase the strength and
durability performance of the resin. The hydroxyl and/or carboxyl
functional groups of the organophosphorus ester compounds form
primary bonds with the hydrocarbon backbone of the polymeric resin
chains so as to join and rigidly connect adjacent chains. Thus, the
cross-linking that accompanies the use of the organophosphorus
esters results in final wood composite materials with increased
strength and durability. Furthermore, the cross-linking reduces the
likelihood that these organophosphorus esters will leach out from
the composite panel.
The fire retardant organophosphorus ester chemicals may be
incorporated into the wood strands that form an oriented strand
board before, during or after the addition of the polymeric binder
resin and wax additive material, but before they are heated and
pressed. The order at which these compounds are applied to the wood
flakes or strands to form the composite material is not essential
to successfully practicing the present invention. There are two
preferable orders of addition. In the first, wax is sprayed or
applied onto the wood strands, and either simultaneous to the
application of the wax or subsequent to the application of the wax,
the organophosphorus ester fire retardant compound is sprayed or
applied onto the wood strands, and lastly the polymeric resin is
sprayed or applied onto the wood strands; in the second preferable
order of addition, the wax is sprayed onto the wood strands, then
the polymeric resin is sprayed or applied, and finally the
organophosphorus ester fire retardant compound is added.
It is preferably to avoid premixing the fire retardant and
polymeric resin because precuring and pre-gelling will occur with
some mixtures of polymeric resins and fire retardants.
Spraying techniques and apparatuses for applying the wax, polymeric
resin, and organophosphorus ester compound are well-known to those
of ordinary skill in the art. A device such as a spray-gun may be
used. However, certain organophosphorus ester compounds may be so
viscous that it is impossible to apply them to wood strands by
spray techniques, and so it is necessary to add viscosity modifiers
to the organophosphorus ester compounds to lower their viscosity
and make them suitable for spraying. As discussed above, FYROL.RTM.
51 can be mixed with FRYOL:DMMP to produce a solution having a
viscosity suitable for spraying. Alternatively, FYROL.RTM. 51 can
be mixed with other chemicals to reduce viscosity, for example, 2
wt % of SURFYNOL.RTM. SF 104 surfactant (manufactured by Air
Products, Inc.), 2 wt % of propanol solution (ACS grade), and 10 wt
% of acetone can be added to FYROL.RTM. 51, with the viscosity of
the resulting organophosphorus ester solution being approximately
400 centipoise.
The invention will now be described with respect to the following
specific, non-limiting examples.
EXAMPLE I
Square OSB panels measuring 50.8 cm on each side, having a target
thickness of approximately 1.11 cm (approximately 7/16 inch), and a
target density of 45 lbs/ft.sup.3, were prepared by mixing
pre-dried wood strands, 2 wt % slack wax, a polymeric binder and
various fire retardant organophosphorus chemicals in the sequential
order detailed below. The wood strands had a moisture content of
about 2 wt % to 3 wt % and the materials were blended in a drum
blender for approximately three minutes. Hot press conditions were
as follows: (1) press closing time: 30 seconds, (2) press cooking
time: 75 seconds, (3) de-gas time: 20 seconds, (4) press control
temperature: 204.degree. C. (400.degree. F.).
For experimental runs 1-12, the strands were made from Yellow
Southern pine. In the process of manufacture, the slack wax was
first sprayed on the wood strands, followed by the fire retardant
organophosphorus chemicals, followed by MDI. For experimental run
13, the slack wax was sprayed upon the wood strands followed by
MDI, however no fire retardant chemical was added to the OSB panel.
Accordingly, the panels of experimental run 13 served as a control
group. In experimental run 14, MDI and Fyrol.RTM. 51 were
pre-blended prior to spraying the mixture upon the wax coated wood
strands, however because pre-gelling occurred shortly after
pre-blending the MDI and Fyrol.RTM. 51 no panels were prepared
under that design condition. For experimental run 15, slack wax was
first sprayed on the wood strands, followed by the MDI, than fire
retardant organophosphorus chemicals. Two OSB panels were prepared
for each design condition.
The loading levels and types of fire retardant chemicals employed
are listed below in Table 1.
TABLE 1 wt % of Organophosphorus Organophosphorus Example No. MDI
wt % ester compounds ester compounds: 1 5 5 Fyrol .RTM. 51 2 5 10
Fyrol .RTM. 51 3 8 5 Fyrol .RTM. 51 4 8 10 Fyrol .RTM. 51 5 5 5
Fyrol .RTM. 6 6 5 10 Fyrol .RTM. 6 7 8 5 Fyrol .RTM. 6 8 8 10 Fyrol
.RTM. 6 9 5 5 Fyrol .RTM.-DMMP 10 5 10 Fyrol .RTM.-DMMP 11 8 5
Fyrol .RTM.-DMMP 12 8 10 Fyrol .RTM.-DMMP 13 5 -- -- 14 5 5 Fyrol
.RTM. 51 15 5 5 Fyrol .RTM. 51
In each of example nos. 1-15, the wt % of organophosphorus ester
compound and polymeric resin compound is based on the oven-dried
weight of the wood flakes and strands.
The OSB samples were subsequently cut into specific sizes and the
following physical properties tested according to the procedure
disclosed in ASTM D1037-98:
(1) Modulus of elasticity (MOE)
(2) Modulus of rupture (MOR)
(3) Internal Bonding (IB)
(4) 24 Hour Thickness Swelling (TS)
(5) 24 Hour Water Absorption (WA)
(6) Density of the tested panels
Although there is no single standard test to determine fire
resistance of various construction materials, flame spread rating
(also known as the "flame spread index") made in accordance with
ASTM D-3806, have acquired common acceptance by various regulatory
agencies. Individual Class Ratings represent a particular range of
flame spread ratings as illustrated below.
Flame Spread Rating Class Rating 0-25 A 25-75 B >75 C
In many states and municipalities it is required that construction
materials for use in commercial or public buildings have a class
rating of `A`. `C` class materials are more commonly used in
residential applications.
Accordingly, the fire retardant properties for each of the
experimental OSB panels prepared in experiment nos. 1-15 were
determined by calculating the flame spread rating (also referred to
as flame spread index) using a 2-foot tunnel-testing machine as
directed by ASTM D-3806.
In addition, fire retardancy was measured by ASTM D-2863 to
determine the limiting oxygen index (LOI). Essentially, the oxygen
index test determines the amount of oxygen in a closed atmosphere
which is required to support the combustion of an OSB panel. In
brief, a specimen of a given composition is placed in a glass
chimney in which a measured oxygen/nitrogen mixture flows upwardly.
The specimen is ignited by means of a pilot flame and the burning
behavior is observed. If the sample burns too rapidly, a new
specimen of the same composition is tested at a lower oxygen
concentration. If the sample does not burn within the prescribed
limits, another new specimen of the same composition is tested at a
higher oxygen concentration. This procedure is used to determine
the lowest oxygen level at which the prescribed limits of the test
are achieved which is defined as the LOI for that composition. The
higher the LOI, the more flame resistant the composition.
Finally, cone calorimeter testing was used in accordance with ASTM
E-1354-94 to determine the peak heat release rate (PHRR), ignition
time (IT), and smoke extinguishing area (SEA).
The results of the above tests for each of the experimental OSB
panels prepared is listed in Table 2, below. The control OSB panel
is prepared by applying the mixture of Example No. 13 (which
contains no organophosphorus ester fire retardant additive) to an
OSB panel. This control OSB panel demonstrated an unfavorably low
LOI of 26.89, and a very high FSI of 120. Conversely, the samples
containing the fire retardant organophosphorus ester demonstrated
superior fire retardant characteristics as compared to the control.
Specifically, comparing the OSB panel of Example No. 13 (no
organophosphorus ester applied) with the OSB panel of Example No.
15 (containing 5 wt % organophosphorus ester) shows that when an
OSB panel contains an amount of organophosphorus ester, the FSI
decreases by nearly 50% (and the corresponding ASTM E-84 fire
safety class rating falls from a C rating to a B rating).
Additionally, the LOI increases by approximately 27% when an
organophosphorus ester is added to the OSB panel. Furthermore, the
OSB panel of Example No. 15 has excellent strength properties, with
a bonding strength of 115 psi.
While the density of each of the OSB panels varied in each of the
examples, such variation is well within the range of densities that
would have been expected by a person of ordinary skill in the
art.
This data surprisingly demonstrates that preparing a wood composite
material that includes wood strands, organophosphorus ester
compounds and polymer binder resins results in a material that has
excellent fire retardant performance.
TABLE 2 Cone Calorimeter Testing (ASTM E- Physical Property Testing
(ASTM E-1037-98) 1354-94) Example Density MOE MOR IB TS % WA % PHRR
IT 60 SEA 60 ML LOI No. (pcf) (psi) .times. 10.sup.3 (psi) (psi) %
% KW/m.sup.2 (second) (m.sup.2 /kg) (g/s*m.sup.2) % FSI 1 41.5 417
4215 43.1 7.90 20.9 237.9 21.1 134.8 17.78 35.23 75.6 2 44.1 500
4042 44.0 7.4 18.1 208.3 14.8 132.4 16.77 37.32 67.8 3 43.9 474
4598 46.5 6.9 17.1 227.3 17.9 142.6 16.74 38.14 62.6 4 45.2 505
4184 56.4 7.2 15.0 236.8 16.5 136.0 17.20 39.96 65.2 5 48.1 720
6272 136 9.1 15.4 264.3 15.3 113.0 17.52 32.33 80.8 6 45.3 565 4400
44.6 18 27.3 246.2 12.3 132.8 17.67 34.13 93.8 7 47.1 568 5080 191
7.8 13.9 242.0 14.7 128.8 16.63 34.64 80.8 8 43.6 607 5230 120 11
15.3 258.8 8.3 137.4 17.72 34.75 93.8 9 42.7 631 5350 104 9.5 15.3
223.2 20.0 212.4 16.13 36.38 80.8 10 44.6 477 3170 32 21 29.9 252.8
17.6 207.2 17.15 37.4 73.0 11 41.7 715 6500 109 12 17.3 220.1 22.0
176.7 16.57 36 86.0 12 47.6 680 5448 143 8.8 17.9 210.7 19.7 185.8
15.47 39.67 65.2 13 52.0 694 6160 161 9.3 14.4 291.3 14.7 114.8
18.66 26.89 120 15 49.4 562 4800 115 7.0 13.9 219.7 14.4 132.4
15.94 34.2 65.2
In the table above "60 MLR" is the average mass loss rate at the
first 60 second after the sample ignites and "60 SEA" is the
average special extinguished area measured at the first 60 second
after the sample ignites.
It will be appreciated by those skilled in the art that changes
could be made to the embodiments described above without departing
from the broad inventive concept thereof. It is understood,
therefore, that this invention is not limited to the particular
embodiments disclosed, but it is intended to cover modifications
within the spirit and scope of the present invention as defined by
the appended claims.
* * * * *